OneTaskBy Tim King · Updated
MP4 to MP3
Pull Audio From MOV, MKV and WebM Files, Faster Than Playing the Video Through
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How the MP4 To MP3 works
This MP4 to MP3 converter saves the sound from an MP4 or another video as an MP3. Pick 128, 192 or 320 kbps and the page decodes the sound track and encodes the MP3 on your device. That runs much faster than playing the video through. It works with MOV, MKV and WebM files too. Nothing is uploaded.
MP4 to MP3: taking the sound out of a video
An MP4 file holds a video track and usually one sound track, most often AAC. MP3 can only hold sound, so the page reads the sound track with Mediabunny, an open-source media library. It decodes the track with WebCodecs and encodes it as MP3 with LAME, the long-standing open-source MP3 encoder. The video track is never decoded, which is why this takes seconds rather than the length of the video.
Choosing a bitrate
- 320 kbps is the highest MP3 bitrate. Use it for music when file size does not matter.
- 192 kbps is transparent for most listeners on most music, at 60 percent of the size.
- 128 kbps is plenty for speech: lectures, podcasts, interviews and voice notes.
The source sound is already compressed, usually as AAC at 128 to 256 kbps. Choosing a higher MP3 bitrate than the source cannot add back detail; it only makes the file bigger. Mono sources stay mono, and sound with more than two channels is reduced to stereo.
Why MP3 rather than keeping the AAC
AAC sound sounds better than MP3 at the same bitrate. But MP3 is the format every car stereo, old music player, DJ tool and podcast host takes without question. To trim the sound or save it as WAV instead, use extract audio from video. For WebM recordings, WebM to MP3 does the same job. To cut the MP3 to a section, use the audio trimmer.
FAQ
How long does it take?
Usually a few seconds per minute of video, since only the sound is decoded. A one-hour lecture typically converts in well under a minute on a recent computer, and a little longer on a phone.
Can I extract sound from a video with no audio track?
No. If the file has no sound track, the page says so. Screen recordings made without a microphone or system audio often have none, so check the recorder's sound settings before the next recording.
Is the MP3 quality the same as the video's sound?
Very close at 192 or 320 kbps. Each conversion between lossy formats loses a little, but at those bitrates the difference is very hard to hear on speakers or headphones.
Is the file uploaded?
No. The conversion runs in this browser tab and the file never leaves your device. The page only needs the internet to load itself and the converter library, and the finished file is saved straight from memory to your downloads.
See also: all Audio & Video tools, Units, Images, Documents, Data & Code.
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